A first example of related art is a phase shifter serving as a dielectric waveguide device that has a coplanar waveguide formed on a ferroelectric thin film and changes the phase of electromagnetic wave by applying a voltage to the ferroelectric thin film (for example, see Japanese Patent Application National Publication JP-A 2003-508942).
A second example of related art is a phase shifter serving as a dielectric waveguide device that has a parallel and flat plate structure with a ferroelectric loaded (for example, see M. Cohn and A. F. Eikenberg, “Ferroelectric Phase Shifters for VHF and UHF,” IRE Trans. on Microwave Theory and Techniques Vol. MTT-10, pp. 536-548 (1962)).
A third example of related art is a phase shifter that controls the phase by controlling a dielectric constant of a part of a dielectric body in a non-radioactive dielectric guide (for example, see Japanese Unexamined Patent Publication JP-A 8-102604 (1996)).
In the first example of related art, the amount of a phase change per unit length is insufficient, and accordingly the line length needs to be long in order to obtain a required phase change. For this reason, the phase shifter is increased in size.
In the second and third examples of related art, there is an attempt to obtain the phase change by using a dielectric body having a variable dielectric constant in the dielectric waveguide, but in this case, the thickness of the dielectric waveguide is increased. For this reason, there is a problem in that a high voltage of 4000 V should be applied.
As such, in the related art, it is difficult to achieve a small and low-voltage operable dielectric waveguide device with a dielectric body which varies in dielectric constant depending on the magnitude of an applied electric field.